A numerical study of a controlled flow evolving in a Taylor-Couette system is presented in this paper. The study is devoted to investigate the effect of the outer cylinder cross-section variation on the flow behavior. It is aimed to make assessment of the flow response in terms of the criticality of the early transitional flow regimes and the accompanying flow topology alterations. The numerical simulations are carried out on the Fluent software package for a three-dimensional incompressible flow. The basic system is characterized by a height H = 200 mm, a ratio of the inner to the outer cylinders radii η = 0.9, an aspect ratio corresponding to the cylinders height reported to the gap length Г = 40 and a ratio of the gap to the radius of the inner cylinder δ = 0.1. The numerical deformation of the outer cylinder is executed using the dynamic mesh program according to a predefined function implemented in a homemade program as an UDF (user defined function). It is established that the first instability mode of transition is retarded from Tac1 = 41.33, corresponding to the first Taylor number critical value, to Tac1 = 70 when the deforming amplitude is equal to 15% the external cylinder diameter value. This flow relaminarization process is accompanied by substantial modifications in the flow behavior and configuration.

Plasma aided materials conversion is the use of charged particles for producing new materials with unusual and superior properties or to convert unwanted materials such as waste into environmentally friendly products. The near LTE plasma (in atmospheric or reduced pressure) is a nice tool for engineering of materials which in consequence upgrades the performance of most of the consumer goods. The paper presents a few samples of the own research results related to the design and use of some plasma reactors for synthesis of nanomaterials and hazardous materials destruction with their conversion into valuable products.

The picosecond ultrasonics technique is used to investigate the viscoelastic properties of nucleus of fixed single osteoblast progenitor cells adhering on a titanium alloy substrate. A two-color probing picosecond ultrasonics and a fluorescence visualization setups were developed and combined to allow to distinguish subcomponents inside the cell under investigation. It opens the way for quantitative measurements of the viscoelastic properties of single cells and of their sub-micrometer thickness. It is shown that a blue probe, λ = 400 nm, is preferable to a red probe, λ = 800 nm, to perform these measurements with fixed sub-micrometer bone cells. 26 GHz acoustic frequencies are detected in cells as thin as 135 nm. A 1D analytical model of the acoustic generation and of the optical detection is used to describe the experimental results. The nucleus longitudinal elastic moduli (13–16 GPa) and dynamic viscosities (13–30 cP) are measured at high frequencies (GHz) from a time-frequency analysis of the experimental data of fixed single cells.

The oil and fat were treated at first by only ozone bubbling and it was confirmed that the collection efficiency of them became 98.4% when the aeration was used. It showed that the aeration method in a grease trap cleared the standard value of 90% and there was no worry on the oil and fat outflow from a grease trap. The characteristics of sonication process were studied for free fatty acids degradation. The free saturated fatty acids are the most hard-degradable compounds of the fats, oils and greases (FOGs) in the grease trap. The influence of various parameters such as immersion level of an ultrasound probe in the liquid and bubbling of various gases (Ar, O2, air, O3) on the sonochemical and energy efficiency of the sonication process was investigated. The most effective degradation treatment method for saturated free fatty acids was the combination of sonication and low flow rate argon bubbling.

This paper presents a stability analysis of a free piston Stirling engine. The model and the detailed calculation of pressures losses are exposed. Stability of the machine is studied by the observation of the eigenvalues of the model matrix. Model validation based on the comparison with NASA experimental results is described. The influence of operational and construction parameters on performance and stability issues is exposed. The results show that most parameters that are beneficial for machine power seem to induce irregular mechanical characteristics with load, suggesting that self-sustained oscillations could be difficult to maintain and control.

Organic materials used for packing food products prevent the access of microorganisms or gases, like oxygen or water vapor. To prolong the stability of products, preservatives such as sulfur dioxide, sulfites, benzoates, nitrites and many other chemical compounds are used. To eliminate or limit the amount of preservatives added to food, so-called active packaging is sought for, which would limit the development of microorganisms. Such packaging can be achieved, among others, by plasma modification of a material to deposit on its surface substances inhibiting the growth of bacteria. In this work plasma modification was carried out in barrier discharge under atmospheric pressure. Sulfur dioxide or/and sodium oxide were used as the coating precursors. As a result of bacteriological studies it was found that sulfur containing coatings show a 16% inhibition of Salmonella bacteria growth and 8% inhibition of Staphylococcus aureus bacteria growth. Sodium containing coatings show worse (by 10%) inhibiting properties. Moreover, films with plasma deposited coatings show good sealing properties against water vapor.

We succeeded in generating an atmospheric pressure Townsend discharge (APTD) in air by using a simple DBD device that consists of alumina barriers and plane electrodes. So far, we applied the APTD to an ozonizer and found that the ozone generation efficiency was higher by the APTD mode than by the conventional DBD mode in larger specific input energy region. It is well known that an operation under an optimized high gas pressure is advantageous for efficient ozone generation from air. In this paper, we investigated whether the Townsend discharge (TD) in dry air in high pressure up to 0.17 MPa can be generated or not. From the observation results of current waveforms and discharge photographs, we found that (1) the discharge currents flow continuously and have only one peak in every half cycle in all gas pressure and (2) filamentary discharges are not recognized between barriers in all gas pressure. These features completely agree with the features of the APTD we reported. Therefore, we concluded that our TD can be generated even in dry air in the pressure range of 0.1 and 0.17 MPa.

We developed a portable ozone-mist sterilization system to exterminate pests (harmful insects) in agricultural field and greenhouse. The system is composed of an ozone generator, an ozone-mist spray and a small container of ozone gas. The ozone generator can supply highly concentrated ozone using the surface dielectric barrier discharge. Ozone-mist is produced using a developed nozzle system. We studied the effects of ozone-mist spray sterilization on insects and agricultural plants. The sterilization conditions are estimated by monitoring the behavior of aphids and observing the damage of the plants. It was shown that aphids were exterminated in 30 s without noticeable damages of the plant leaves. The reactive radicals with strong oxidation potential such as hydroxyl radical (*OH), hydroperoxide radical (*HO2), the superoxide ion radical (*O2‒) and ozonide radical ion (*O3‒) can increase the sterilization rate for aphids.

Changes of the gas temperature in a single microdischarge channel and inside the entire discharge gap of dielectric barrier discharge were analyzed. It was shown that the initial temperature of the gas in the microdischarge channel is tens of degrees higher than the average gas temperature in the gap. The gas expanding effect which causes the gas mixing in the reaction space is presented. It has been explained why and in which part of the gap the ozone is decomposed.

Formation of negative ions initiated by interaction of thermal electrons and in the corona discharge (CD) in N2 with small admixture of SF6; was studied using the ion mobility spectrometry- orthogonal acceleration time-of-flight mass spectrometry (IMS-oaTOF) at atmospheric pressure. The negative ions have been analyzed by the ion mobility spectrometry and mass spectrometry (IMS-MS) and two-dimensional spectra (2D IMS-MS) have been recorded. We discuss the mechanisms of the negative ion formation in the N2/SF6 mixtures (0.003-0.018%) as well as the transport parameters of the ions in these mixtures. The values of the reduced ion mobilities of negative ions formed in these mixtures were determined (2.43 cm2/V s for HF2– (HF)n, 2.32 cm2/V s for NO3– (HF)n, 2.08 cm2/V s for SF5–, 2.01 cm2/V s for SOF5–, 2.00 for SOF4– 1.99 cm2/V s for SF6–, 1.83 cm2/V s for SOF5–(H2O)n and 1.73 for SOF5–(H2O)n(HF)m). The assignment of the ion mobility peaks was performed on the basis of the 2D IMS-MS spectra.

The modular device for the waste utilization, using the pyrolytic-plasma method, consists of, among others, the plasma reactor operating on the gliding discharge principles. The reactor is applied to oxidize hydrocarbons created in the process of the waste pyrolysis. Thus, the plasma reactor operation influences significantly the qualitative and quantitative composition of the output gases. Finding the most advantageous construction of the plasma reactor and the process parameters ensures full and complete oxidation of hydrocarbons. In the waste utilization process, two streams of gases were introduced into the plasma reactor through the system of two coaxial nozzles. The first stream was a mixture of argon and hydrocarbons and the second one was oxygen. Two different methods of gas introduction were considered. Methane was used as a model hydrocarbon both in calculations and in the experiments. On the basis of numerical calculations (Fluent commercial program), it was found that the most advantageous method of gas introduction into the reactor was the one in which the mixture of argon and hydrocarbons was introduced through the central nozzle and the oxygen was introduced through the outer one. This conclusion was confirmed experimentally.

Atmospheric pressure plasma jet (APPJ) was developed for decontamination purposes. Features of the device are ability to work with various feed-gases at the atmospheric pressure in several gas-flow, frequency and current-voltage regimes. LabVIEW virtual measurement sub-system for monitoring and measurement process through subsequent setting of electrical and gas-flow parameters (digital control of flow-meters), conditioning and amplification of electrical signals and collection of the data from peripheral measuring devices was applied.

Advanced oxidation processes, especially induced by non-thermal plasmas, are widely known for their high sanitation efficiency. The paper presents general overview of atmospheric pressure plasma jet (APPJ) reactors for bactericidal decontamination purposes. In the conclusion part, the basic requirements for APPJ as a tool for biomedical applications including the treatment of living tissues are highlighted.

The decomposition of CCl4 in air was investigated at atmospheric pressure in a new type of dielectric barrier discharge reactor. The reactor was powered by three different power supplies: pulsed of low frequency (150–600 Hz), pulsed of 15 kHz frequency with regulated current pulse duration and AC of 6.8 kHz frequency. Maximum conversion of CCl4 depended on the power supply. 64, 87 and 98% were the maximum achieved conversions of CCl4 for tested power supplies. The products of CCl4 conversion and energy consumption depended on power supply system. The chlorine gas was always the main product obtained from CCl4. The smallest energy consumption (~0.3 kWh per mol CCl4 converted) was achieved for pulsed power supply system of low frequency. It was 26 and 230 times less than energy consumption (for similar overall CCl4 conversion) in AC of 6.8 kHz frequency and pulsed of 15 kHz frequency respectively.

Two different methods of deposition of thin layers containing titanium and barium with the use of dielectric barrier discharge were investigated. The first was carried out in two stages. The first stage consisted in transferring compounds containing titanium and barium from the vapor of the organic precursor to the copper substrate, while the second stage involved the etching of the organic layer in oxygen. The second method consisted in transferring titanium and barium to the copper substrate from the ceramic plate made of barium titanate, which was one of the electrodes during the plasma process. The results of analysis obtained by SIMS showed directly that both methods gave a positive result in the deposition of the thin layers containing a certain amount of titanium and barium on the surface of the copper plate. However, more effective method was that involving the properties of reaction with the metallorganic precursor. FTIR study of the layers prepared from the organic precursor indirectly showed that layers deposited on the copper plate contained compounds of barium and titanium. FTIR study also revealed that during the process of etching in oxygen, the organic layer was decreased, but it was not completely removed.

An investigation of atmospheric pressure argon DBD plasma jet generated at 6 kHz sinusoidal voltage was carried out. On the basis of recorded electrical, optical and spectral characteristics spatiotemporal evolution of plasma jet in negative and positive half-cycles of voltage was studied. It was found that the dynamics of argon jet propagation outside the tube differs considerably from that found by other authors in the case of helium jet. The difference was explained with the influence of Penning reactions between metastable state He atoms and air molecules in He jet. On the basis of radiative transitions N2 (C-B, 0-0) and OH(A-X, 0-0) the rotational temperatures of N2(C, 0) and OH(A, 0) were estimated along jet axis. In regions where Ar-air mixing was negligible or low, the rotational temperatures of both molecules coincide and were close to the gas temperature.